Process for producing allyl ether

ABSTRACT

In the production of allyl ethers of polyol by reacting a straight-chain polyol compound with an allyl halide in the presence of an alkali metal hydroxide, wherein the straight-chain polyol compound has carbon atoms each having one hydroxyl group, the reaction between the straight-chain polyol compound and the allyl halide is proceeded in the presence of water having the amount dissolving the straight-chain polyol compound at a reaction temperature, then 14% by mol, based on total molar amount of a hydroxyl group contained in the straight-chain polyol compound, of the allyl halide is added to a reaction system before at least part of water is released out of the reaction system.

TECHNICAL FIELD

The present invention relates to a method of industrially andpractically producing allyl ethers of straight-chain polyol in a highyield.

RELATED ART

Hitherto, some documents propose a technology of allyl-etherifying apolyol. Examples of a document disclosing the method ofallyl-etherifying a polyol having a non-straight-chain structure (abranched-chain polyol) are as follows. JP-B-04-4303 discloses that anallyl alcohol is added as an accelerating agent when allyl ethers ofpentaerythritol are prepared. In addition, JP-B-03-80141 discloses amethod of adjusting the total amount of water added to a reaction systemwhen allyl ethers of trimethylolpropane are prepared.

As to a polyol having a straight-chain structure, JP-A-57-81418discloses a method of using a tetrabutyl ammonium acidic sulfate salt asa phase transfer catalyst. However, this method has many industrialdisadvantages in view of the defect that a step of removing a catalystis necessary, and the defect that it is necessary to adopt a measure foravoiding the incorporation of a catalyst or a residue thereof into aproduct.

Since the straight-chain polyol has extremely large hydrophilicity, asolvent for largely dissolving the straight-chain polyol in a practicallevel is substantially limited to water. Even if it is intended that thestraight-chain polyol is reacted with an allyl halide and an alkalimetal hydroxide under the reaction conditions that water is completelyabsent, the reaction hardly proceeds or does not proceed at all. Thus,the reaction is proceeded by dissolving the straight-chain polyol inwater, but the contact between the straight-chain polyol and the allylhalide is poor at the beginning of the reaction so that the reactionhardly proceeds. Even if an accelerating agent such as allyl alcohol isused, the reaction of the straight-chain polyol hardly proceeds incomparison with the branched-chain polyol such as pentaerythritol sothat it was difficult to produce the allyl ether of polyol from thestraight-chain polyol at the industrially practical level.

Although the presence of water is necessary at the beginning of thereaction, water causes the decrease of a reaction rate and thegeneration of a hydrolysis reaction of the allyl halide so that theyield is decreased. Thus, JP-B-4-4303 discloses a method of distillingoff water in a reaction system at the stage when the reaction ratebecomes large, in the preparation of allyl ether of pentaerythritol frompentaerythritol and allyl chloride. However, this method is successfulfor pentaerythritol which a branched-chain polyol, but, when used for astraight-chain polyol, this method was insufficient in the yield, thecomplicated post-treatment due to insolubility of the residualstraight-chain polyol, the control of distribution of allylation numberand average allylation number of the product, and the period of time forwhole reaction.

SUMMARY OF THE INVENTION

The present inventors intensively studied a method of preparing an allylether of polyol from a straight-chain polyol compound, which method hasthe excellent productivity at an industrially practical level, the highconversion of raw materials and the high yield of the product.

The present inventors carefully observed the step of reacting allylchloride by only reflux without discharging water; discovered that, whenat least 14% by mol, based on 1 mol of a hydroxyl group of thestraight-chain polyol compound, of the allyl chloride is added, asufficient amount of an oil layer is rapidly formed by thehydrophobization caused by allylation and the raw material, sorbitol issufficiently decreased at this time, the raw material substantiallydisappears, even if the process is shifted to a dehydration step.

The present invention provides a method of producing allyl ethers ofpolyol by reacting a straight-chain polyol compound with an allyl halidein the presence of an alkali metal hydroxide, wherein the straight-chainpolyol compound has carbon atoms each having one hydroxyl group, and isrepresented by the general formula (1):HOCH₂[CH(OH)]_(n)CH₂OH  (1)wherein n is an integer of from 2 to 6,characterized in that the reaction between the straight-chain polyolcompound and the allyl halide is proceeded in the presence of waterhaving the amount dissolving the straight-chain polyol compound at areaction temperature, then 14% by mol, based on total molar amount of ahydroxyl group contained in the straight-chain polyol compound, of theallyl halide is added to a reaction system before the discharge of waterout of the reaction system is initiated.

The transfer to the dehydration step at an earlier stage is usuallyadvantageous to prevent the reaction rate decrease caused by lowerconcentration of alkaline hydroxide and the increase of side reactions.However, if the process shifts to the dehydration step before at least14% by mol of allyl chloride is added and reacted, sorbitol having highwater-solubility, which remains at that time, tends to remain unreacted.

DETAILED EXPLANATION OF THE INVENTION

The method of the present invention is generally conducted by adding theallyl halide to a reaction vessel (or a reaction zone) which contains awhole amount of the straight-chain polyol compound.

In one embodiment of the present invention,

-   (A) the straight-chain polyol compound, the alkali metal hydroxide    and water having an amount dissolving the straight-chain polyol    compound at a reaction temperature are added into the reaction    vessel,-   (B) at least part of the allyl halide is added to the reaction    vessel so that the reaction between the straight-chain polyol    compound and the allyl halide is initiated, and then-   (C) after at least 14% by mol, based on total molar amount of the    hydroxyl group contained in the straight-chain polyol compound, of    the allyl halide is added to the reaction vessel, the release of    water out of the reaction vessel is initiated.

In the formula (1) of the straight-chain polyol compound, the number ofn may be particularly from 2 to 4. Examples of the straight-chain polyolcompound are a straight-chain sugar alcohol, particularly erythritol,xylitol and sorbitol.

Examples of the allyl halide are allyl chloride and allyl bromide.

Examples of the alkali metal hydroxide are lithium hydroxide, sodiumhydroxide and potassium hydroxide.

In the present invention, the allyletherification reaction of thestraight-chain polyol compound is preferably conducted by adding theallyl halide to the reaction system (that is, reaction vessel)containing whole amount of the straight-chain polyol compound to bereacted. The addition of the allyl halide may be conducted continuouslyor intermittently. For example, the allyl halide may be dropwise added,or whole amount of the allyl halide may be divided into several (forexample, 3 to 20) small portions and said small portions may be addedone after another.

In the present invention, water is present in the amount for dissolvingthe straight-chain polyol compound at the reaction temperature, during aperiod of time between the initiation of allyletherification reactionand the beginning of discharge of water out of the reaction system. Thisdoes not exclude the state that at least part or whole of the used allylhalide is present at the initiation of allyletherification reaction.

After the initiation of the reaction, water may be added so that wholeof the straight-chain polyol compound is dissolved at the reactiontemperature. Water is preferably present before the initiation of theallyletherification reaction in such amount that whole of thestraight-chain polyol compound is dissolved at the reaction temperature.Water may be appropriately added during the proceeding of the reaction.

The amount of water present in the reaction system may be at least 20%by mol, for example 20 to 250% by mol, particularly 100 to 220% mol,especially 140 to 180% by mol, based on mol of total hydroxyl groupscontained in the straight-chain polyol compound. When the amount ofwater is sufficient for dissolving the straight-chain polyol compound,the speed of the allyletherification reaction is large.

The present invention does not limit the amount of the alkali metalhydroxide introduced into the reaction system until the time at whichthe discharge of water out of the reaction system is initiated. Saidamount of the alkali metal hydroxide may be from 26 to 100% by mol, forexample 28 to 75% by mol, particularly 28 to 60% by mol, more preferablyfrom 30 to 45% by mol, particularly preferably from 30 to 42% by mol,based on mol of total hydroxyl groups contained in the straight-chainpolyol compound. The alkali metal hydroxide may be charged in thenecessary amount before the reaction or may be appropriately addedduring the reaction proceeding. The added alkali metal hydroxide may bein the form of a solid or an aqueous solution. Generally, the alkalimetal hydroxide is added in the form of the aqueous solution in whichthe alkali metal hydroxide is dissolved in water.

Water is not discharged out of the reaction system until at least 14% bymol, based on mol of total hydroxyl groups contained in thestraight-chain polyol compound, of the allyl halide is introduced intothe reaction system. After at least 14% by mol, preferably at least 16%by mol, more preferably at least 18% by mol, particularly at least 20%by mol of the allyl halide is into the reaction system, the discharge ofwater is initiated. At the time when the desired amount of the allylhalide is introduced into the reaction system, an oil layer in thesufficient amount for dissolving the straight-chain polyol compound israpidly formed by the hydrophobization caused by allylation and theamount of the raw material, the straight-chain polyol compound issufficiently decreased. Therefore, even if the dehydration is conducted,the reaction of the straight-chain polyol compound sufficientlyproceeds.

If the discharge of water is initiated earlier (i.e., before the givenamount of the allyl halide is introduced into the reaction system), thestraight-chain polyol compound having no allylation remains in a largeamount in the final reaction product so that by-products are present ina large amount and a product distribution is broad. Even if a refinementprocedure such as washing and distillation is conducted to give a sharpproduct distribution, the conversion of raw materials is low at thereaction completion, the decrease of yield cannot be prevented, andearlier initiation of water discharge is economically disadvantageous.

The discharge of water out of the reaction system can be conducted by,for example, distillation.

In the present invention, the temperature of the allyletherificationreaction is, for example, from 70° C. to 130° C. The time of theallyletherification reaction is, for example, from 8 hours to 24 hours.A period of time between the initiation of the allyletherificationreaction and the initiation of the discharge of water is, for example,from 2 hours to 14 hours.

The allyl ethers of polyol obtained by the method of the presentinvention have at least two allyl groups. The allyl ethers generallyhave at least one hydroxyl group and at least two allyl groups. Thenumber of hydroxyl groups is at least one, for example at least two, andspecific example of the number of hydroxyl groups is from 1 to 4. Thenumber of allyl groups is at least 2, for example at least 3,particularly from 3 to 5. In the case of the mixture of hydroxypolyallylethers, an average number of hydroxyl groups is at least 0.5, forexample at least 1.0, particularly at least 1.5, and an average numberof allyl groups is at least 2.0, for example at least 2.5, particularlyat least 3.0. The number of allyl groups (including the average numberthereof is determined by gas chromatography and NMR (particularly, ¹HNMR).

The allyl ethers of polyol can be used as a crosslinking agent and thelike.

PREFERRED EMBODIMENTS OF THE INVENTION

Hereinafter, the present invention is illustrated with reference to thefollowing Examples and Comparative Examples.

Example 1

859 g of a 70% aqueous solution of D-sorbitol, 583 g of a 48% of anaqueous solution of sodium hydroxide and 60 mL of allyl alcohol werecharged into a 2,000 mL reactor equipped with an agitator, a reflexcondenser, a thermometer and two dropping funnels, and the mixture washeated. At the time when the temperature became 90° C., the dropwiseaddition of allyl chloride from one dropping funnel was initiated. Theamount of the dropwise addition of allyl chloride was controlled toadjust the reaction temperature to at least 70° C. while whole amount ofthe reflux liquid is returned to the reactor.

The addition of 200 g of allyl chloride was completed at 3.7 hours afterthe reaction initiation, the addition of allyl chloride was continued.The time required for the addition of 300 g of allyl chloride was 5.5hours after the reaction initiation. At this time (at the time when 20%by mol, based on total mol of hydroxyl group contained in D-sorbitol, ofallyl halide was added), a water metering reservoir was attached betweenthe reflux condenser and the reactor so that the reflux liquid isseparated to return the oil layer alone to the reactor. The timerequired for the addition of totally 459 g of allyl chloride was 8 hoursafter the reaction initiation. At this time, the dropwise addition of333 g of a 48% aqueous solution of sodium hydroxide from a differentdropping funnel was initiated. The time required for the addition oftotally 842 g of allyl chloride was 11 hours after the reactioninitiation. The temperature was in the range between 70° C. and 90° C.After matured for 1 hour, the reaction mixture was cooled.

The reaction product was a slurry which was a mixture of a yellowishbrown oil and solid particles, and a water layer was absent in thereaction product. After distilled off low-boiling-point materials, theoil was analyzed by gas chromatography and ¹H NMR. The composition (% byweight) was as follows. D-sorbitol: 0.0%, D-sorbitol monoallyl ether:0.4%, diallyl ether: 11.3%, triallyl ether: 35.4%, tetraallyl ether:40.5%, pentaallyl ether: 12.9%, hexaallyl ether: 0.2%. An average molarnumber of allyl groups added to one molecule of D-sorbitol was 3.5.

Comparative Example 1

859 g of a 70% aqueous solution of D-sorbitol, 417 g of a 48% of anaqueous solution of sodium hydroxide and 60 mL of allyl alcohol werecharged into a 2,000 mL reactor equipped with an agitator, a reflexcondenser, a thermometer and two dropping funnels, and the mixture washeated. At the time when the temperature-became 90° C., the dropwiseaddition of allyl chloride was initiated. The amount of the dropwiseaddition of allyl chloride was controlled to adjust the reactiontemperature to at least 70° C. while whole amount of the reflux liquidis returned to the reactor. The addition of 200 g of allyl chloride wascompleted at 7 hours after the reaction initiation. At this time (at thetime when 13% by mol, based on total mol of hydroxyl group contained inD-sorbitol, of allyl halide was added), a water metering reservoir wasattached between the reflux condenser and the reactor so that the refluxliquid is separated to return the oil layer alone to the reactor. Thetime required for the addition of totally 306 g of allyl chloride was10.5 hours after the reaction initiation. At this time, the dropwiseaddition of 500 g of a 48% aqueous solution of sodium hydroxide from adifferent dropping funnel was initiated. The time required for theaddition of totally 842 g of allyl chloride was 14.5 hours after thereaction initiation. The temperature was in the range between 70° C. and90° C. After matured for 1 hour, the reaction mixture was cooled.

The reaction product was a slurry which was a mixture of a yellowishbrown oil and solid particles, and a water layer was absent in thereaction product. After distilled off low-boiling-point materials, theoil was analyzed by gas chromatography and ¹H NMR. The composition (% byweight) was as follows. D-sorbitol: 18.3%, D-sorbitol monoallyl ether:0.2%, diallyl ether: 7.3%, triallyl ether: 25.5%, tetraallyl ether:34.9%, pentaallyl ether: 13.6%, hexaallyl ether: 0.2%. An average molarnumber of allyl groups added to one molecule of D-sorbitol was 3.0.

Effect of the Invention

The present invention provides a method of preparing an allyl ether of astraight-chain polyol, which method has the excellent practicalproductivity at an industrial level and the high conversion of rawmaterials. In the present invention, the following advantageous effectsare achieved:

-   1) The yield is increased.-   2) The complication of post-steps caused by insolubility of the    remaining straight-chain polyol compounds is eliminated.-   3) The distribution of allylation number and the average allylation    number can be excellently controlled.-   4) The total production time can be shortened.

1. A method of producing allyl ethers of polyol by reacting astraight-chain polyol compound with an allyl halide in the presence ofan alkali metal hydroxide, wherein the straight-chain polyol compoundhas carbon atoms each having one hydroxyl group, and is represented bythe general formula (1):HOCH₂[CH(OH)]_(n)CH₂OH  (1) wherein n is an integer of from 2 to 6,characterized in that the reaction between the straight-chain polyolcompound and the allyl halide is proceeded in the presence of waterhaving the amount dissolving the straight-chain polyol compound at areaction temperature, then at least 14% by mol, based on total molaramount of a hydroxyl group contained in the straight-chain polyolcompound, of the allyl halide is added to a reaction system before thedischarge of water out of the reaction system is initiated.
 2. Themethod according to claim 1, wherein (A) the straight-chain polyolcompound, the alkali metal hydroxide and water having an amountdissolving the straight-chain polyol compound at a reaction temperatureare added into the reaction vessel, (B) at least part of the allylhalide is added to the reaction vessel so that the reaction between thestraight-chain polyol compound and the allyl halide is initiated, andthen (C) after at least 14% by mol, based on total molar amount of thehydroxyl group contained in the straight-chain polyol compound, of theallyl halide is added to the reaction vessel, the release of water outof the reaction vessel is initiated.
 3. The method according to claim 1,wherein the allyl halide is allyl chloride, and the alkali metalhydroxide is sodium hydroxide.
 4. The method according to claim 1,wherein the straight-chain polyol compound is selected from the groupconsisting of erythritol, xylitol and D-sorbitol.
 5. The methodaccording to claim 1, wherein the straight-chain polyol compound isD-sorbitol.